Differential mechanism



Y L. E. WINTER 2,824,453

DIFFERENTIAL MECHANISM Feb. 25, 1958 Filed June 11, 1956 INVENTOR.

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United Statesv Patent Ofiice 2,824,453 Patented Feb. 25, 1958 DIFFERENTIAL MECHANISM Lloyd E. Winter, Cedar Rapids, Iowa, assignor to Collins Rfailio Company, Cedar Rapids, Iowa, a corporation owa Application June 11, 1956, Serial No. 590,477

5 Claims. (Cl. 74-1054) This invention relates to a mechanical movement for converting rotary motion into linear motion and more particularly to" a device which will convert two rotary motions into a single linear motion with'a differential relationship between the two rotary motions.

Prior art mechanisms for moving tuning slugs in a radio receiver have utilized coarse and fine tuning of some sort. The usual form has been that of two knobs used to drive different shafts in the gear train used to position the tuner of the receiver. The prior art devices have been undesirable in several respects. It has not been advantageous to have both knobs moved at the same time in that the dials used and theircalibration indicate improperly the frequency tuned. Further, an undesirable relationship exists between the fine and coarse motions in that one must depend on the other gearing for part of its gear Further, the backlash and other errors were difficult to eliminate cheaply.

Accordingly, it is an object of this invention to provide a device which permits gross adjustment of a linear motion by one rotary input motion and provides a fine adjustment of the same linear motion by a separate rotary input.

It is an object of this invention to provide a mechanical movement for use in tuning devices for radio equipment.

It is a feature of this invention that simple, easily-made parts are utilized in its manufacture.

It is a further feature of this invention that the efiect of the separate rotary motions superimpose independently of each other, without disturbing the setting of the other.

Further objects, features, and advantages of the invention will become apparent from the following description and claims when read in conjunction with the drawing, in which the figure shows a perspective view of the invention showing the mechanism with tuning slugs mounted thereon In the figure a slug table or support means is supported by four racks. Racks 11 and 12 support the table centrally. Racks 13 and 14 support the slug table at one end. All racks are pivotally connected to the slug table. The pivot pins 9 of the racks 11 and 12 extend into the guide slots 15, in projections 36 of base 35, to prevent side sway of the slug table. Only one projection 36 is shown, to avoid a confusion of detail. The racks are substantially parallel, and have a linear motion with this same relationship. On slug table 10 are mounted a plurality of slugs 16.

These slugs 16 are tuning slugs composed of a magnetic material and which are suspended within the central portions of a series of coils, not illustrated. The position of the slugs relative to the coils establishes the tuning characteristic of the coils.

A coarse motion shaft 17 has mounted thereon a gear 18 and two small pinions 19 and 20. Gear 18 and pinions 19 and 20 are fixed to shaft 17. Pinions 19 and 20 engage racks 12 and 11, respectively. Shaft 17 is mounted fixedly to base 35 by bearings 21. A second shaft 22 extends substantially parallel to shaft 17. Mounted on and fixed to shaft 22 is a gear 23 with substantially the same tooth characteristics as gear 18 and meshing therewith. Pinions 24 and 25, similar to pinions 19 and 20, are fixed to shaft 22 also. The four pinion gears have substantially the same tooth characteristics as the four racks respectively meshing therewith.

Mounted on shafts 17 and 22 and extending transversely thereto are arms 26 and 27. These arms are pivoted about shaft 17 and move freely thereon. Shaft 22 is carried solely by arms 26 and 27 and is free to rotate in holes or bearings mounted on the arms. On the ends of arms 26 and 27 radially outward from the pivot of shaft 17 beyond shaft 22 are gear segments 28 and 29, respectively.

A third shaft 31 is the fine motion control. Mounted on shaft 31 and fixed thereto are two pinions 32 and 33 of like characteristics. Pinions 32 and 33 mesh with gear segments 28 and 29. The pitch diameter of gear segments 25are thusrotated. The rotation of these pinions causes both sets of racks to move at the same speed up or down depending on the direction of rotation of the pinions. Since the racks are held in substantially parallel relationship, the slug table will be moved up and down parallel to an original position. Whatever fine adjustment setting was previously made is not disturbed by this coarse motion.

Rotation of the fine adjustment shaft 31 rotates pinions 32 and 33. This rotates movable arms 26 and 27 pivotally about shaft 17. This carries shaft 22 in a small movement about shaft 17. It is readily seen that with shaft 17 stationary, pinions 24 and 25 will lift racks 14 and 13 directly and the rotation of gear 23 about gear 18 will cause an additional rotation of shaft 22 with further motion of the racks in the same direction.

The motion of racks 13 and 14 separately relative to racks 11 and 12 cause the slug table to tilt slightly. For slugs on one side of the pivot 9, this will mean a slight motion downward whereas slugs on the other side of the pivot will be moved slightly upward. It is obvious that this motion may be'used for slugs mounted in any position relative to the pivot with the radius from the pivot controlling the amount of motion. The fine adjustment does not disturb the coarse setting; thus the dial calibration will remain true for both fine and coarse settings at any combination.

Application of the invention to a radio receiver results in coarse adjustment by shaft 17 establishing the particular band of frequencies, e. g. integral megacycles, to which the receiver is tuned. The fine adjustment, shaft 31, then tunes the receiver over a much narrower range of frequencies, e. g., within the megacycle band selected by the coarse tuning shaft 17. Since the tuning motion is made linear, the megacycle adjustment may be detented and indicated by simple counters, with each megacycle variation tuned by the fine control with a continuous rotary adjustment and a similar counter.

For relatively small angular motions of gear segments 28 and 29, deviation from true linearity does not rise above a tenth of one percent. The deviation is of the same order of magnitude as the deviation of the value of 0 in radians from the value of sine 0.

Although this invention has been described with respect to particular embodiments thereof, it is not to be so limited because changes and modifications may be madetherein which are within the full intended scope of the invention as defined by the appended claims.

I claim:

1. A differential mechanism comprising a support means, means for moving said support means parallelly including a pair of shafts, said pair of shafts being coupled to said'support means by racks and pinions, means for moving said support means a minute amount comprising means for moving one of said shafts relative to the other.

2. A differential mechanism comprising support means, said support means having a guide for linear motion, a pair of shafts, said shafts being coupled together, rack and pinion means coupling said shafts to said support means for linear motion of said support means, one of said shafts being adapted for coupling to external motion, and means for moving the other of said shafts relative to said one substantially along the direction of the rack means.

3. The mechanism of claim 2 wherein said last-named means is a pair of arms mounted on said pair of shafts pivoting about said one of said pair of shafts, said arms having gear sectors at the ends thereof, and a third shaft having gears meshing therewith, whereby rotation of said third shaft provides a tilting of the support means.

4. A differential mechanism comprising support means supported for linear motion, first rack means pivotally mounted on said support means, second rack means pivotally mounted on said support means, said first and second rack means being substantially parallel and movable in a direction substantially parallel to the motion of said support means, a first shaft, a second shaft, 2. third shaft, each 4 shaft being substantially parallel to the other, means coupling said first and second shafts together, pinion means on said first and second shafts engaging said first and second rack means respectively whereby rotation of said first shaft moves said first and second rack means at substantially the same speed, arm means pivoted about said first shaft, said arm means rotatably mounting said second shaft, said arm means having a gear segment on one end opposite said pivot, gear means mounted on said third shaft, said gear means engaging said gear segment, whereby motion of said third shaft moves said second shaft rela tive to said first shaft.

5. A differential mechanism comprising a base, a first, second, and third shaft, said first and third shafts being supported on said base, arm means pivoting on said first shaft, said arm means mounting said second shaft, means coupling the end of said arm means to said third shaft, means rotatably coupling said first and second shafts, slug carrying means, rack and pinion means coupling said slug carrying means to said first and second shafts, whereby rotation of said first shaft moves said slug carrying means parallelto itself and rotation of said third shaft rotates and said slug carrying means about a coupling point.

References Cited in the file of this patent UNITED, STATES, PATENTS 1,833,235 Slocumb Nov. 24, 1931 FOREIGN PATENTS 500,611 Germany June 23, 1930 

